Francium (Fr) has the highest atomic radius in the periodic table. It belongs to the alkali metals group. Its atomic number is 87. The periodic trend of atomic radius suggests that the atomic radius usually decreases along a period (left to right) and increases down a group (top to bottom).

Therefore, the capacity of a parallel plate capacitor directly depends on the relative permittivity of dielectric material, the permittivity of space, the area of plates, and is inversely dependent on the separation between the plates.

The correct order of radiations is in descending order of frequencies.

 X-rays > Infrared > Microwaves > Radio waves

The damping force of an oscillating particle is observed to be proportional to velocity. The constant of proportionality can be measured in. kgs−1.